OFFSET
1,1
COMMENTS
In A000027, if n, n+(n-1) and n+(n+1) are composite, then n is a term of this sequence.
Suggestion: there are arbitrarily long sets of consecutive integers, e.g., 632..637, 665..672, 6428..6443.
MATHEMATICA
Select[Range[2, 1000], !PrimeQ[2#-1]&&!PrimeQ[#]&&!PrimeQ[2#+1]&]
Select[Range[250], AllTrue[{#, 2#-1, 2#+1}, CompositeQ]&] (* Harvey P. Dale, Feb 26 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Sep 21 2011
STATUS
approved